Precision Force Control for Tensioning and Calendering

When purchasing a hybrid vehicle or full electric vehicle, few buyers consider the impact that the Lithium-Ion battery will have on the user’s experience. Rechargeable Lithium-Ion batteries are common in consumer electronics and battery electric vehicles. The quality of the battery effects the duration of the charge that is held and the amount of use a consumer has between charges.

First a little about Li-Ion battery manufacturing. There are two popular techniques, stacking and winding. Of the two techniques, winding produces the most efficient batteries by weaving together positive and negative layers. Winding machines tension control to provide a constant pull of a web or filament through the machine, to ensure consistent material tension in the process. Difficulties arise in the process since the tensioning forces need to be very responsive and precisely controlled.

Currently, most Lithium-Ion battery manufacturers use 20th century technology, consisting of low friction air cylinders and electro-magnetic regulators. Air is compressible but electrons are not, so precise forces cannot be held pneumatically. Bad batteries are scrapped, creating costly waste. Batteries that were not rejected are often weak, unable to hold a charge efficiently.

One high-end Lithium-Ion industrial battery manufacturer in China has found a method of improving the quality of their Li-Ion batteries through use of SMAC mechatronic actuators. To make the most energy-efficient Lithium-Ion batteries, programmable tensioning is required, decreasing tension as the weave thickens. In a closed loop system as with SMAC, the web tension is measured and this information is fed back real time to a controller. If the tension varies from a predetermined value or range, the controller automatically adjusts the tension.

SMAC mechatronic actuators have light moving masses compared to pneumatics and programmable force, speed, and position, can provide 10x lower variation in force. The result is even distribution of tension, a much better weave and more efficient batteries. Additionally, the battery manufacturer’s scrap and waste is reduced, lowering their costs.

This same moving coil actuator technology has spread to consumer electronics. A large consumer electronics in Korea uses the same technique for tablets, phones, and other small devices. Other European battery manufacturers are winding very small coils using SMAC devices for ulta-precise tension control.